Detent



April21, 1959 N. F. sMlTH v `DETENT Filed March 27, 1956 f IN1/ENT NESTOR F SM/ United States Patnt DETENT Nestor F. Smith, Ithaca, N.Y., assignor to Ithaca Gun Company, Incorporated, Ithaca, N.Y., a corporation of New York Application March 27, 1956, Serial No. 574,119

1 Claim. (Cl. 42-16) This invention relates to detents for temporarily holding a movable part of a mechanism in a certain position. For example, it may be applied to a gun to hold the breech bolt in an open or safety position, as well as to other machines involving a similar combination of direct and transverse forces. While this detent mechanism is of general application in many elds, it will be described here by way of illustration in connection with rearms such as shot guns and riiles in which it can be used with advantageous results.

The average sportsman likes to have a gun around the house but is well aware of the hazards of accidents, particularly if there are children in the family. There is always the chance that a gun might have been left in a loaded condition. Accordingly it is generally considered good practice to leave the receiver open when the gun is not in Ause so that its empty condition can be seen at a glance. Many forms of locks and detents have been devised for that purpose, usually involving the additional complication of catches or locking elements which take some time or extra manual operations to release. While desiring safety, the average gunner also likes an arm that can be loaded and red quickly without delay or excess motions. The present invention is intended to accomplish those results, and is neat and convenient.

A form of detent frequently found on machinery consists of a plunger which a light spring forces into a socket or depression of the element which is to be temporarily` restrained from motion. In order to release it `the detent can be pulled out, or in some cases can be pushed out by extra force applied to the locked element, as in the line spacing detent pawl of a typewriter platen for example. In those rare cases where a spring tends to pull the plunger out of engagement instead of force it into engagement, additional locking catches have hadgto be provided; otherwise the plunger would spring out to the released position and unlock the restrained element whenever ones linger was removed from the head of the plunger. Such additional locking catches, when required to hold the detent down in place, are objectionable to some Sportsmen, as being unduly complicated and slow in action.

The form of detent in the present invention has a spring urging it outward to release it instead of inward to lock it; but to hold the detent in, that spring is so proportioned to other existing forces that the detent will remain in place until such other forces are diminished by natural operations not involving special catches. Such a detent is particularly convenient on a gun, as will be described.

Referring now to the drawings forming part of this specification- Fig. 1 is a cross-sectional view of the detent as applied to a gun, showing the gun bolt forward and the detent in the unlocked position.

Fig. 2 is a similar view showing the detent in the locked position, with the gun bolt drawn back against a heavy spring.

Similar reference numerals refer to similar parts thruout the various views.

In the drawings there are shown the appropriate portions of a gun or riile 1 having a breech bolt 2 operating in the chamber of the receiver 3 where it can be drawn back by any suitable means against the force of the cornpression spring 4 as is common in guns, and held in the retracted position by a detent 5 as shown in Fig. 2. The foregoing general parts in one form or another are found in most guns and their usual operation need not be further described. When it is desired to use the gun it can be loaded, the detent 5 released, and the bolt 2 then moves forward under the impetus of the spring 4 or a manual operation, forcing the cartridge 7 into place for tiring.

The present invention is particularly directed to the operation of the detent 5 which holds the bolt 2 from moving until it is released. In a typical embodiment as shown in Fig. 1 and Fig. 2 this detent 5 consists of a plunger 10 having an external button or head 11 at one end and an internal head or locking tip 12 at the other end. This plungers internal portion extends thru a hole 14 in the wall of the chamber 3, the axis of the hole 14 and plunger 10 being substantially perpendicular to the longitudinal axis of motion of the bolt 2, whlch in most guns is also the line of the barrel. In any event, for the purpose of operation to be described, the

travel of the detent must be transverse to the travel of the bolt or other element that is to 'be detained by the detent; and such bolt or mechanical element must be under a continual force tending to move it transversely across the line of motion of the detent, for frictional reasons to be described.

In this gun for example the reciprocating bolt 2 which slldes along its longitudinal axis in the receiver chamber 3, has on the periphery of the bolt a small socket or depression 15 slightly larger than the tip 12 of the detent plunger 10 so that the tip can tit easily therein. Toward the other end, generally external of the gun, the plunger 10 is provided with a lange or collar 17 under which is located a spring 18 tending to force the plunger 10 outward away from the socket 15, such outward movement being limited by the ange or casing 20 thru which the outer neck of the detent plunger 10 extends to the operating button or head 11. When the chamber is closed the bolt 2 is at the left as shown in Fig. 1.

When the -bolt 2 is drawn back in the receiver 3 as shown in Fig. 2, the socket depression 15 in the bolt c omes into line with the detent plunger 10 so that the tip 12 of the detent can be forced into it by pressing down the button 11 by hand. This will lock the bolt back and hold the chamber open so long as the button is held down. It would appear however that this lock would cease to operate when ones linger was removed from the button, due to the fact that the spring 18 is continually tending to force the plunger tip 12 out of the socket so as to release the detent. Such undoubtedly would be the case if the spring 18 were constructed with that purpose in mind. However, in the present invention the spring 18 is purposely made relatively weak and other forces are utilized in such a manner as to hold the detent in locking position by overcoming the effect of the spring 18 until the operator chooses to use the gun. Such a result is obtained without encumbering the gun with special locks, catches or similar latchng or holding attachments.

For the purpose of holding the detent in a locked position, the locking mechanism uses a light spring 18 on the button in combination with the much stronger spring 4 on the bolt. The greater force of the spring 4 operating thru friction of the bolt 2 on the side of the plunger 10 Patented Apr. 21, 1959 overcomes the force of the spring 18 and holds the locking tip 12 in place in the socket 15.

To release the lock, the operator merely pulls on the bolt 2 in the same manner as in operating the gun. Then the bolt, being already substantially at the end of its rearward travel, only moves imperceptibly; but the pull of the operators hand offsets the force of the compression spring 4 momentarily so as to reduce the frictional effect of the bolt on the side of the locking plunger 10, thus allowing the spring 18 to move the plunger outward so that the tip 12 is pulled out of the socket 15. The gun is thereby unlocked for operation. Thus with fewer parts than have been used in the past an improved result is obtained.

`In the application of the detent to an ordinary gun as described, a simple form of socket 15 can be made by drilling an appropriate hole 14 thru the wall 3 and part way into the Abolt 2 at its withdrawn position. Such a hole drilled a short distance into the bolt will provide a suliiciently vertical wall to give the necessary frictional restraint to the plunger of the detent. However, various other forms of sockets and plungers may be used, provided that their contacting faces afford suliicient friction to hold the locking detent in place. Furthermore, the socket need not even be of the same configuration as the locking element, provided it affords suflicient friction. For example, in some guns the front face of the bolt may serve as a socket; in other types the bolt should be free to rotate as well as slide, and in such a case a peripheral groove may be cut around the bolt or a collar may be provided. The frictional face need not necessarily have the same slope or angle in the detained member as in the detent, so long as the difference does not exceed a working angle of friction that will hold it. Also the detent plunger may be canted slightly and the holding face it engages may be undercut correspondingly if desired, since only a slight withdrawal of the locked element is required to release it in any event. When the holding face is undercut the preponderance of the transverse force against the side of the detent is not so critical, but nevertheless such force should be definitely greater than that of the detent releasing spring, in order to prevent the detent from rattling in its socket or jumping out.

The force used to produce the necessary friction on the side of the detent need no-t necessarily be a spring such as 4, as any constant force that can be depended upon may lbe utilized, provided that it will produce a sufficient friction on the side of the detent 12 to hold it in locked position against the force of the releasing spring 18. This improved type of detent is therefore applicable not only to guns or reciprocating action but also to any mechanism in which the forces in the locked and locking elements are transverse to each other, with the force of the locked element sufficiently greater than the strength of the detent spring of the locking element so as to attain the desired result.

While I have in the foregoing described a certain specific embodiment by way of example, it will be understood that it is merely for the purpose of illustration to make clear the principles of the invention, which is not limited tothe particular form shown but is susceptible to vario-us modifications and adaptations in different installations as will be apparent to those skilled in the art without departing from the scope of the invention as stated in the following claim.

I claim:

In a firearm, the combination of a receiver and a movable breech bolt therein, a spring for moving said bolt to a closed position, a detent for holding said bolt in an open position against the force of said spring, said detent comprising a plunger extending thru an opening in the receiver transverse to the direction of movement of the bolt, the inner end of said plunger serving as a locking element for the ybolt and the outer end of said plunger serving as a push button for locking the detent in holding position, said bolt having a socket to receive the inner end of the plunger when the bolt is in open position, a coil compression spring for said detent of a strength insufficient to retract the detent when the bolt is under pressure of the bolt spring, said coil compression spring continuously urging said plunger outward so as to tend to withdraw it from said socket, said socket and plunger having cooperating pressure faces transverse to the direction of motion of the bolt proportioned so that the holding force of the bolt spring predominates over the releasing force of the detent spring when pressure on the push button is released and the button is held in locking position by predominant friction, whereby the detent can be held in locking position until the force of the main spring on the bolt is reduced so that the detent spring can withdraw the detent plunger to release the bolt.

References Cited in the le of this patent UNITED STATES PATENTS 1,664,049 Sedgley Mar. 27, 1928 1,975,809 Teitscheid Oct. 9, 1934 2,181,131 Johnson Nov. 28, 1939 2,422,853 Reising June 24, 1947 2,659,994 Yale Nov. 24, 1953 2,692,557 Wales Oct. 26, 1954 2,705,921 Moseman Apr. 12, 1955 FOREIGN PATENTS 79,515 Switzerland Dec. 2, 1918 

